Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
  • C07C45/51—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by pyrolysis, rearrangement or decomposition
  • C07C45/53—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by pyrolysis, rearrangement or decomposition of hydroperoxides

Definitions

• This invention relates to the preparation of hex-2-enal.
• U.S. Pat. No. 3,839,457 describes a process for the preparation of hex-2-enal by subjecting cyclohexyl hydroperoxide in the liquid phase to the action of an aqueous solution of a palladium derivative.
• Cyclohexyl hydroperoxide can be prepared from cyclohexanol or by oxidation of cyclohexane in the liquid phase, without a catalyst, using a molecular oxygen containing gas, optionally in the presence of agents which can complex the metal ions. Processes of this type are described for example in French Pat. Nos. 1,404,723 and 1,491,518.
• the hydroperoxide can be purified by known methods such as conversion to the sodium salt and treatment with carbon dioxide.
• the palladium derivative used as the catalyst in the decomposition of the hydroperoxide can be a palladium halide such as, for example, a chlorinated derivative.
• the amount of catalyst is generally chosen so as to provide 1 to 20 gram atoms of elementary metal per 100 mols of hydroperoxide.
• the organic solvents which can be used in the decomposition of the hydroperoxide can be a linear ether; an ester such as a lower alkyl alkyl- or aryl-carboxylate; or a hydrocarbon such as an alkane or alkene with 6 to 20 carbon atoms, a cycloalkane or cycloalkene with 5 to 16 carbon atoms in the ring, optionally substituted by one or more alkyl radicals with 1 to 4 carbon atoms; benzene or its derivatives which are mono-substituted or poly-substituted by chlorine or fluorine, or an alkyl radical with 1 to 4 carbon atoms or a group such as an alkoxy group with 1 to 4 carbon atoms, a cyano group or a nitro group, or a phenyl radical derived from one of the substituted derivatives of benzene described above.
• the amounts of water and, where appropriate, of organic solvent employed in the decomposition of the hydroperoxide are such that the proportion by weight of hydroperoxide in the reaction mixture is between 2% and 50%, and preferably between 5 and 30%.
• the weight of water is at least of the order of 1% relative to the weight of the organic solution.
• This palladium catalysed process gives good yields, but requires relatively long reaction times in order to achieve a high degree of decomposition of the hydroperoxide; its use thus leads to relatively low productivity of the deperoxidation plant. It was therefore desirable to have available a process for the preparation of hex-2-enal which overcomes this low productivity problem whilst retaining the advantages, particularly the good yields, of the palladium catalysed process described above.
• the present invention provides a process for the preparation of hex-2-enal which comprises subjecting cyclohexyl hydroperoxide in the liquid phase to the action of an aqueous solution containing both a palladium derivative and a catalytic amount of a derivative of divalent iron.
• the deperoxidation may optionally be carried out in the presence of an organic solvent for the hydroperoxide, the organic solvent being one which is immiscible with water.
• the derivatives of iron-II used in the invention are those which are soluble in or which have been rendered soluble in water under the reaction conditions.
• the radical associated with the iron is not critical insofar as it fulfils these solubility conditions.
• Salts of inorganic acids, and especially ferrous sulphate, ferrous nitrate of ferrous chloride, are generally used.
• Ferrous chloride tetrahydrate is preferably used to form the aqueous solution used in the process according to the invention.
• the amount of the derivative of iron-II used expressed as the number of gram atoms of elementary metal per 100 mols of hydroperoxide is not critical and normally can be between 0.01 and 20; more precisely, this amount is chosen within the above-mentioned range so that it provides the reaction medium with a number of gram atoms of elementary iron which is at most equal to the number of gram atoms of palladium.
• the palladium derivative used in the invention can be any one of those used in the process described in the above-mentioned Patent Specification, e.g. halogenated derivatives of palladium such as alkali metal or alkaline earth metal halogenopalladates which are soluble in water, and particularly alkali metal chloropalladates such as sodium chloropalladate.
• halogenated derivatives of palladium such as alkali metal or alkaline earth metal halogenopalladates which are soluble in water, and particularly alkali metal chloropalladates such as sodium chloropalladate.
• the general working conditions of the present process are apart from the use of the ferrous derivative, substantially the same as those used in the process described in the above-mentioned Patent Specification and reference should be made to the above-mentioned Patent Specification for further details of the general working conditions.
• cyclohexyl hydroperoxide can be introduced, in the pure state, into the aqueous solution of the metal derivatives at a temperature from 50° C., up to the boiling point of the mixture; if it has been decided to use an organic solvent, this can be added to the aqueous solution employed.
• the hydroperoxide in the form of a solution in the organic solvent chosen.
• the aqueous phase containing the metal catalysts can be introduced into a solution of cyclohexyl hydroperoxide in cyclohexane, heated beforehand to between 50° C., and the boiling point of the mixture.
• the reaction is generally carried out by bringing the pH of the aqueous phase to a value of between 0 and 4, and preferably of approximately 1, by adding a strong acid.
• the reaction mixture is kept at the desired temperature until the hydroperoxide employed has been completely decomposed.
• the hex-2-enal can then be recovered from the reaction mixture by procedures substantially similar to those described in the above-mentioned Patent Specification and once again, reference should be made to the Patent Specification for full details.
• aqueous solution containing the amounts of sodium chloropalladate (Na 2 PdCl 4 ) and ferrous chloride tetrahydrate (FeCl 2 .4H 2 O) specified below, is brought to a pH of approximately 1 by addition of a small amount of hydrochloric acid.
• the acidified catalyst solution and cyclohexane is then introduced into a 2 liter glass reactor equipped with a central stirrer, a reflux condenser, a dropping funnel and a thermometer.
• This mixture is heated to the desired temperature, generally its characteristic boiling point, and the purified cyclohexyl hydroperoxide is then added as rapidly as possible to the mixture which is stirred at the chosen temperature for the specified period of time, until the peroxidic oxygen has completely disappeared.
• reaction mixture is cooled, filtered and thereafter decanted.
• the aqueous phase is extracted with diethyl ether.
• the combined organic phases are distilled and the ether and part of the cyclohexane are removed during this process.
• the balance of the reaction that is to say the yields, relative to the pure cyclohexyl hydroperoxide introduced, of hex-2-enal, cyclohexanol and cyclohexanone formed is determined by vapour phase chromatographic analysis.
• the cyclohexane oxidation product contains 40 g. (0.345 mol) of pure cyclohexyl hydroperoxide in addition to other products such as cyclohexanol (13.3 g.) and cyclohexanone (6.73 g.); the remainder consists mainly of cyclohexane.
• This mixture is heated to a temperature of about 73° C.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
• Catalysts (AREA)

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Citations (3)

• 1974
  • 1974-06-06 FR FR7419550A patent/FR2273789A2/fr active Granted
• 1975
  • 1975-05-22 GB GB22092/75A patent/GB1492107A/en not_active Expired
  • 1975-05-29 NL NL7506372A patent/NL7506372A/xx unknown
  • 1975-06-04 JP JP50066631A patent/JPS516915A/ja active Pending
  • 1975-06-05 BE BE157067A patent/BE829919A/xx unknown
  • 1975-06-05 US US05/584,118 patent/US4028420A/en not_active Expired - Lifetime
  • 1975-06-05 CH CH726175A patent/CH602536A5/xx not_active IP Right Cessation
  • 1975-06-06 IT IT24118/75A patent/IT1038770B/it active
  • 1975-06-06 DE DE19752525336 patent/DE2525336A1/de active Pending

Patent Citations (3)

Non-Patent Citations (3)

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